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Ell-one and ell-infinity are not reflexive
Statement refuted
Assume AC. The classical sequence spaces and are reflexive.
Facts & Assumptions
AC holds (The Axiom of Choice).
Under the ultrafilter lemma, DC, and Hahn--Banach, real and complex are not reflexive (Ell one is not reflexive).
Under Hahn--Banach and Countable Choice, is reflexive exactly when is reflexive (A Banach space is reflexive if and only if its dual is reflexive).
The real dual of is (Counting measure specializes the representation theorem to and ), and the same holds over the complex field (The complex continuous dual of ell-one is ell-infinity).
The dual is isometrically , and under AC the countably additive charges form its proper subspace (The dual of ell-infinity is ba, The countably additive part of ba is ell-one).
Counterexample
Given: The objects and hypotheses in the Statement.
AC in [A1] supplies the ultrafilter lemma, DC, Hahn--Banach, and Countable [given, A1, L1, L2] Choice needed by [L1] and [L2]. Thus [L1] already refutes reflexivity of , over both scalar fields.
By [L3], . If were reflexive, [given, L3, L2, step 1.1] the reverse implication in [L2] would make reflexive, contradicting step 1.1. Hence is not reflexive.
Independently, [L4] exhibits the bidual surplus: under the identification [given, L4, A1, step 2.1] , the canonical image is only the proper subspace of countably additive charges. This is a concrete failed- surjectivity witness consistent with steps 1.1-2.1.
Depends on
- The Axiom of Choice
- A Banach space is reflexive if and only if its dual is reflexive
- Ell one is not reflexive
- Counting measure specializes the representation theorem to $\ell^p$ and $\ell^q$
- The complex continuous dual of ell-one is ell-infinity
- The dual of ell-infinity is ba
- The countably additive part of ba is ell-one
Used by
Nothing in the library uses this result yet.
Dependency tree · two levels
24 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- Michael Müger, Introduction to Functional Analysis (standard reference, not scraped)